SUMMARY/ABSTRACT Our long term goal is to reduce oral health disparities in rural school children. Our immediate goal is to test two new evidence-based, school-based, cavity prevention programs. We will compare two preventions: (1) A newer, simpler, less expensive, efficient treatment using fluoride varnish + silver diamine fluoride; and (2) A more traditional, complex, expensive, time-intensive treatment that includes simple + sealants + interim therapeutic restorations. The simpler method takes 6 minutes to deliver, compared to the more complex method that takes 20 minutes. Therefore, if the simpler, less expensive is as effective as the more complex, more expensive method, the data could support clinical and policy change. To compare the two methods we will use a cluster randomized control trial design. We will implement this program in rural New Hampshire schools. All children in a school with informed consent will receive the same treatment (either simple or complex). We will provide preventive care twice per year for the 5 year grant period. We will follow all children longitudinally for five years to determine the effectiveness of each preventive method. The primary outcome to make this determination will be the percentage of children with untreated decay. This is one of the U.S. Healthy People oral health goals. We will also examine the cost and cost- effectiveness. This will allow us to determine the balance between effectiveness and cost. Assessing effectiveness and costs is particularly important for reducing disparities. If an intervention is quick, inexpensive, and 100% effective, that is a relatively simple choice. Most interventions are not 100% effective. Therefore, information on time, expense, and effectiveness will allow us to make better informed clinical and policy decisions. Specifically, this will help us answer the question: How much of which preventive intervention will increase access, improve health, and reduce costs?